Differential mechanism for positioning a type character on a type element

ABSTRACT

A type element, which is mounted for movement along a writing line and has a plurality of types arranged thereon, is rotated through a differential mechanism to position a selected type at the printing position. The differential mechanism includes a first gear connected to the type element through a rotatably supported shaft. A sector gear meshes with the first gear to rotate the first gear in one direction in accordance with inputs to an arm on which the sector gear is mounted. The arm is pivotally connected by a pin to a link, which is pivotally mounted about the axis of the first gear, so that movements of the link change the position of the pin, which is the axis of rotation of the sector gear and is intermediate the sector gear and the input end of the arm, to rotate the first gear in the opposite direction. The inputs to the link and the arm are supplied through separate lever arrangements, which may be actuated by a single driving means or by separate pneumatically controlled means.

tlnited States Patent Schaeier v [4 1 May 30, 1972 [72] Inventor: John 0. Schaefer, Lexington, Ky.

[73] Assignee: International Business Machine Corporation, Armonk, NY.

[22] Filed: June 29, 1970 [21] Appl. No.: 50,480

Cralle eta] ....197/16 UX Gassino et al ..l97/17 Primary Examiner-Robert E. Pulfrey Assistant Examiner-R. T. Rader AttorneyHanifin and Jancin and Frank C. Leach, J r.

[5 7] ABSTRACT A type element, which is mounted for movement along a writing line and has a plurality of types arranged thereon, is rotated through a differential mechanism to position a selected type at the printing position. The differential mechanism includes a first gear connected to the type element through a rotatably supported shaft. A sector gear meshes with the first gear to rotate the first gear in one direction in accordance with inputs to an arm on which the sector gear is mounted. The arm is pivotally connected by a pin to a link, which is pivotally mounted about the axis of the first gear, so that movements of the link change the position of the pin, which is the axis of rotation of the sector gear and is intermediate the sector gear and the input end of the arm, to rotate the first gear in the opposite direction. The inputs to the link and the arm are supplied through separate lever arrangements, which may be actuated by a single driving means or by separate pneumatically controlled means.

18 Claims, 3 Drawing Figures Patented May 30, 1972 2 Sheets-Sheet 1 FIG. 1

INVENTOR.

JOHN 0. SCHAEFER ATTORNEY.

Patented May 30, 1972 3,666,070

2 Sheets-Sheet 2 DIFFERENTIAL MECHANISM FOR POSITIONING A TYPE CHARACTER ON A TYPE ELEMENT It has previously been suggested to use a single type element having types arranged in at least one row thereon about the periphery of the type element. This arrangement enables fast rotational positioning of a type at a printing position.

One previously suggested selection mechanism for positioning one of the types on the type element at the printing position has employed a mechanical digital to analog convertor that was mounted on the machine frame. The convertor delivered analog motion from the frame to a laterally movable carrier on which the type element was supported. The mechanism occupied considerable space and demanded much of the mechanical components to achieve reliability.

The present invention is an improvement over the previously suggested selection mechanism. The mechanism of the present invention reduces space and component requirements by delivering digital information directly into the type element carrier. A new compact convertor construction enables mounting within the moving carrier itself.

The convertor of the present invention utilizes convertor differential mechanism for combining two independent motions for rotating the type element to one of a selected plurality of positions. As a result of two different inputs driving meshing gears in opposite directions, any wear on the meshing gears is substantially the same so that the mechanism inherently compensates for any wear.

An object of this invention is to provide a differential mechanism for positioning a type on a type element at a printing position.

Another object of this invention is to provide a movable type element having its positioning mechanism supported for movement therewith.

The foregoing and other objects, features, and advantages of the invention will be more apparent from the following more particular description of preferred embodiments of the invention as illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a bottom perspective view of the mechanism for positioning a type element.

FIG. 2 is a side elevational view, partly in section, of a type selection mechanism for use with the positioning mechanism of the present invention.

FIG. 3 is a schematic sectional view, partly in elevation, of another means for supplying the inputs to the differential mechanism of FIG. 1.

Referring to the drawings and particularly FIG. 1, there is shown a type element supported for movement relative to a fixed platen 11 on a carrier 12. The carrier 12 may be moved by known mechanism such as that shown in US. Pat. No. 2,9 I 9,002 to Palmer, for example.

The type element 10 has a connecting shaft or positioning member 14 connected thereto and rotatably supported by the carrier 12. A gear 15 is connected to the shaft 14 for transmitting rotary motion of the gear 15 through the connecting shaft 14 to the type element 10. Thus, by rotating the gear 15 in the correct direction, any one of types 16, which could be numbers and/or symbols, for example, can move along a path to a printing position defined in cooperation with the platen 1 1.

The gear 15 meshes with a sector gear 17, which is integral with an arm 18. The arm 18 has a slot 19 therein with the sector gear 17 formed on one surface thereof, and the gear 15 is disposed within the slot 19 whereby there can be relative movement between the gear 15 and the arm 18.

The arm 18 is pivotally mounted by a pin or axle 20, which is fixed to a modifying link 21. The modifying link 21 has one end pivotally mounted about the axis of the connecting shaft 14.

It should be understood that the distance between the axis of the gear 15 and the axis of the pin or axle 20 is constant. Furthermore, the axis of the pin or axle 20 is the center of the pitch diameter of the teeth of the sector gear 17.

The pin 20 is connected to the modifying link 21 between its pivotal connection with the shaft 14 and a pin 22, which pivotally connects the other end of the modifying link 21 to an input lever means 23, which provides an input to the modifying link 21. Any input to the modifying link 21 by the lever means 23 pivots the modifying link 21 clockwise about the shaft 14 and against the force of a spring 24, which has one end secured to the modifying link 21 by being connected to the pivot pin 22 and its other end secured to a portion 25 of the carrier 12.

At the same time that the modifying link 21 is receiving an input from the lever means 23, the arm 18 is receiving an input from an input lever means 26, which is pivotally connected to the end of the arm 18 by a pin 27. The input to the arm 18 from the input lever means 26 always pivots the arm 18 clockwise about the pin 20 whereby any motion of the lever means 26 rotates the pinion gear 15 clockwise. The movement of the arm 18 by the lever means 26 is opposed by a spring 28, which has one end secured to the lever means 26 and its other end fixed to a portion 29 of the carrier 12.

Any movement of the modifying link 21 clockwise about the shaft 14 moves the pivot pin 20 of the arm 18 therewith whereby the arm 18 is carried counterclockwise about the pin 27. As a result of this movement of the arm 18, the gear 15 is rotated counterclockwise to rotate the type element 10 counterclockwise. This is the opposite to the clockwise rotation of the gear 15 produced by the clockwise movement of the arm 18 about the pin 20 by the lever means 26.

The input to the modifying link 21 from the lever means 23 and to the arm 18 from the input lever means 26 is supplied synchronously from a single drive cam30 fixed on a sleeve 31, which is keyed to a print shaft 31 for rotation therewith while being slidable relative thereto. The print shaft 31' is driven during each print cycle.

The lever means 23 includes a link 32, which is pivotally connected to the modifying link 21 by the pin 22 and through a pin 33 to one end of a link 34. The link 34, which is pivotally mounted on a portion 35 of the carrier 12 by a pivot pin 36, has its other end connected through a pivot pin 37 to a link 38. The link 38 has a finger 39 thereon for radial positioning for cooperation with one of a plurality of concentric radially spaced face cam surfaces 40, 41, 42, and 43 on the drive cam 30.

When the finger 39 is in engagement with the cam surface 40, which has the maximum axial rise, five units of motion are delivered to the lever means 23. The cam surface 41 of the drive cam 30 produces three units of motion of the modifying link 21 when the finger 39 is in engagement therewith. Only one unit of motion of the modifying link 21 occurs when the finger 39 engages the cam surface 42 of the drive cam 30. When the finger 39 is in engagement with the cam surface 43, no motion is imparted to the modifying link 21 from the lever means 23.

The motion to the lever means 23 from the drive cam 30 is provided through rotation of the drive cam 30 causing axial motion of the link 38 of the lever means 23 to the left to pivot the link 34 clockwise about the pivot pin 36. This pulls the link 32 to the right whereby the modifying link 21 is pivoted clockwise about the axes of the shaft 14 and the gear 15.

The lever means 26 includes a link 44, which has one end connected to the arm 18 by the pivot pin 27 and its other end connected by a pivot pin 45 to a link 46. The link 46 is pivotally mounted on the portion 35 of the carrier by the pivot pin 36. The other end of the link 46 of the lever means 26 is connected through a pivot pin 47 to a link 48, which has a finger 49 on its end for cooperation with one of the cam surfaces 40-43 of the drive cam 30.

In the same manner as described for the lever means 23, the lever means 26 can impart either five, three, one, or zero units of motion to the arm 18 depending upon which of the face cam surfaces 40-43 is engaged by the finger 49 of the lever means 26. It should be understood that the fingers 3,9 and 49 cannot both engage any one of the cam surfaces 41-43 simultaneously, but both of the fingers 39 and 49 can engage the cam surface 40 simultaneously.

The radial position of each of the fingers 39 and 49 relative to the face cam surfaces 40-43 is controlled by a plurality of selector earns 50, 51, and 52, which are slidably mounted on the sleeve 31. The selector cams 5052 have a key 53 cooperating with a keyway 54 in the sleeve 31 to allow any of the cams 50-52 to slide along the sleeve 31 while rotating therewith.

The cam 50 can cooperate with either a projecting finger 55 on the link 38 of the lever means 23 or a finger 56 on the link 48 of the lever means 26 to select the cam surface 41, which produces three units of motion. The cam 50 also can be disposed to not engage either of the fingers 55 and 56.

The cam 50 is positioned by a bifurcated end of a bellcrank 57, which is pivotally mounted on a portion 58 of the carrier by a pivot pin 59. Thus, when the selector cam 50 is to engage the finger 55, the bellcrank 57 is pivoted clockwise about the pivot pin 59 by a torque bar 60. When the bellcrank 57 is pivoted counterclockwise by the torque bar 60, the selector cam 50 is disposed for cooperation with the finger 56 on the link 48 of the lever means 26.

If the bellcrank 57 is not activated, then the selector cam 50 remains disposed between the fingers 55 and 56 as shown in FIG. 1. Thus, this provides a neutral or third position whereby neither of the links 38 and 48 is controlled by the selector cam 50.

The link 38 is continuously urged clockwise about the pivot pin 37 by a spring 61, which has one end connected to the link 38 and its other end fixed to a portion of the carrier 12. This urges the finger 39 into engagement with one of the cam surfaces 40-43 of the cam 30 and the finger 55 into engagement with the cam 50 if the bellcrank 57 has been pivoted clockwise.

Similarly, a spring 63, which has one end fixed to the link 48 and its other end secured to the same portion of the carrier 12 as the spring 61, continuously urges the link 48 clockwise about the pivot pin 47. This continuously urges the finger 49 toward one of the cam surfaces 40-43 of the drive cam 30. Furthermore, the spring 63 urges the finger 56 into engagement with the selector cam 50 when the cam 50 is moved to the left along the sleeve 31 by counterclockwise pivoting of the bellcrank 57.

When the finger 55 engages the cam 50, the finger 39 of the link 38 is moved into engagement with the cam surface 41 whereby three units of motion are imparted to the modifying link 21 during a revolution of the drive cam 30. If the finger 56 cooperates with the cam 50, then the finger 49 is moved into engagement with the cam surface 41 of the drive cam 30 to impart three units of motion to the arm 18 during a revolution of the drive cam 30.

The selector cam 51 cooperates with a finger 64 on the link 38 or a finger 65 on the link 48 to select the cam surface 42, which produces one unit of motion. The cam 51 may be positioned in the neutral position as shown in FIG. 1 whereby it does not engage either of the fingers 64 and 65 or may be moved to the right to engage the finger 64 or to the left to engage the finger 65.

The axial position of the cam 51 on the sleeve 31 is determined by a bellcrank 66, which is pivotally mounted by a pin 67 on the portion 58 of the carrier 12. A torque bar 68 controls the movement of the bellcrank 66 in the same manner as the torque bar 60 controls the movement of the bellcrank 57.

When the selector cam 51 is in engagement with the finger 64, the finger 39 of the link 38 engages the cam surface 42 of the cam 30. Accordingly, this transmits one unit of motion to the modifying link 21 when the cam 30 is rotated through one revolution. Likewise, if the cam 51 is in engagement with the finger 65 of the link 48, the finger 49 of the link 48 is moved into engagement with the cam surface 42 of the cam 30 to impart one unit of motion to the arm 18 when the cam 30 rotates through one revolution. Of course, the cam 51 may be in the neutral position as shown in FIG. 1 so as to not engage either of the fingers 64 and 65.

The selector cam 52 cooperates with a finger 69 on the link 38 or a finger 70 on the link 48 to select the cam surface 43, which produces no axial motion. The axial position of the cam 52 is determined by a bellcrank 71, which is pivotally mounted by a pivot pin 72 on the portion 58 of the carrier 12. A torque bar 73 controls the position of the bellcrank 71 in the same manner as the torque bar 60 controls the position of the bellcrank 57.

If the cam 52 is engaging the finger 69, the finger 39 of the link 38 is in engagement with the cam surface 43 on the cam 30. The cam surface 43 does not have any rise thereon whereby the rotation of the cam 30 does not impart any axial motion to the link 38 so that there is no motion to the modifying link 21; this produces the zero unit of motion.

Likewise, if the selector cam 52 is in engagement with the finger 70 on the link 48, then the finger 49 of the link 48 is moved into engagement with the cam surface 43 on the drive cam 30 by the spring 63. When this occurs, there is no motion of the link 48 so that there is no motion of the arm 18; this is the zero unit of motion.

During the selection of any one of the types 16 on the type element 10, only one of the selector cams 50-52 is permitted to engage a finger on one of the links 38 and 48 and only one of the selector cams 50-52 can engage a finger on the link 48. Furthermore, if the cam 50 engages the finger 55 on the link 38, then it cannot engage the finger 56 on the link 48.

It should be understood, however, that all of the selector cams 50-52 can be disposed as shown in FIG. 1 so that none engages any of the fingers on the link 38 or any of the fingers on the link 48. When this occurs, the spring 61 moves the finger 39 of the link 38 into a position for cooperation with the cam surface 40. This imparts five units of motion in an axial direction to the link 38 whereby the modifying link 21 is moved five units of motion clockwise about the axes of the shaft 14 and the gear 15.

If none of the fingers on the link 48 engages any of the cams 50-52, then the finger 49 is engaged with the cam surface 40 of the cam 30 by the spring 63. This also imparts five units of motion to the arm 18 whereby the type element 10 does not rotate because two separate five units of motion are producing movement of the gear 15 in opposite directions.

Since only one of the selector cams 50-52 can cooperate with only one of the fingers on the link 38 and only one other of the cams 50-52 can cooperate with only one of the fingers on the link 48, this insures that only one of the fingers 39 and 49 can engage any one of the cam surfaces 41-43 of the drive cam 30. However, when none of the cams 50-52 is engaging any of the fingers of the links 38 and 48, the fingers 39 and 49 of the links 38 and 48, respectively, are moved inwardly sufficiently by the springs 61 and 63, respectively, to engage the cam surface 40. Thus, only the cam surface 40 of the cam surfaces 4043 can be engaged by both of the fingers 39 and 49 simultaneously.

It should be understood that the selector cams 5052 always return to the position shown in FIG. 1 at the end of each print cycle. Thus, the fingers 39 and 49 of the links 38 and 48, respectively, are always disposed for cooperation with the cam surface 40 of the drive cam 30 at the end of each print cycle. Thus, the fingers 39 and 49 of the links 38 and 48, respectively, are always disposed for cooperation with the cam surface 40 of the drive cam 30 at the end of any print cycle. As a result, this is the home position of the type element 10, and the type element 10 is returned to the home position at the end of each print cycle.

The use of the three selector cams 50-52 and the four cam surfaces 40-43 on the drive cam 30 enables eleven of the types 16 in a row on the type element 10 to be presented at the printing position. Thus, the type element 10 can remain at the home position during a print cycle whereby the type 16 at the home position is presented at the printing position. Likewise, the type element 10 can be rotated from one to five units in a clockwise direction or from one to five units in a counterclockwise direction.

These units of rotation of the type element and the direction of rotation are produced by the following relations between the inputs to the arm 18 and the modifying link 21:

As previously mentioned, the torque bar 60 controls the bellcrank 57. The torque bar 60 is pivotally mounted on the fixed frame of the typewriter by a rod 75. A lever 76 and a rod 77 connect the torque bar 60 to a keyboard bail 78 for movement therewith. The keyboard bail 78, which is pivotally mounted on a pin 79, has a stud 80 projecting from one end thereof and to which one end of the rod 77 is connected so that the position of the bail 78 determines the movement of the torque bar 60.

The movement of the torque bar 68 is controlled by the position of a keyboard bail 81 which is pivotally mounted on a pin 82 and connected through a rod 83 to the pivotally mounted torque bar 68 in the same manner as the rod 77 is connected to the torque bar 60. The movement of the torque bar 73 is controlled by the position of a keyboard bail 84, which is pivotally mounted on a pin 85 and is connected through a rod 86 to the pivotally mounted torque bar 73 in the same manner as the rod 77 is connected to the torque bar 60.

During each selection of one of the types 16, each of the bails 78, 81, and 84 may be moved clockwise, counterclockwise, or remain stationary. The motion, if any, to each of the bails 78, 81, and 84 is generated during each print cycle by one of a plurality of keyboard interposers 87 when the interposer 87 is moved through a right to left operating stroke by depression of its associated key lever (one shown at 88 in FIG. 2) as is fully described in U.S. Pat. No. 3,086,635 to Palmer.

Each of the interposers 87 has a projection 89, which engages a bail 90 to initiate operation of a filter shaft 91 in the manner more particularly shown and described in the aforesaid Palmer patent, U.S. Pat. No. 3,086,635. It is the rotation of the filter shaft 91 that causes the right to left operating stroke of the interposer 87 in FIG. 2. The particular interposer 87, which is actuated during a print cycle, depends upon the type 16 that is to be selected.

Each of the interposers 87 has a rear projection 92, a center projection 93, and a forward projection 94. The rear projection 92 is disposed adjacent the bail 78 for cooperation therewith, the center projection 93 is disposed adjacent the bail 81 for cooperation therewith, and the forward projection 84 is located adjacent the bail 81 for cooperation therewith.

Counterclockwise (as viewed in FIG. 2) pivoting of any of the bails 78, 81, and 84 is produced only when the cooperating projection on the interposer 87 has an upper lug 95 thereon for engaging the bail during the right to left operating stroke of the interposer 87. Clockwise (as viewed in F IG. 2) pivoting of any of the bails 78, 81, and 84 is produced only when the cooperating projection on the interposer 87 has a lower lug 96 thereon for engaging the bail during the right to left operating stroke of the interposer 87.

Each of the interposers 87 is coded in accordance with the type 16 that is to be selected by the actuation of the particular interposer 87. Each of the interposers can have only one of the upper lugs 95 and one of the lower lugs 96 so that one of the bails 78, 81, and 84 remains stationary. The interposer 87 also may be devoid of the upper lug 95 and/or the lower lug 96 so that one or both of the other of the bails 78, 81, and 84 remains stationary depending on the type 16 to be printed.

With the interposer of FIG. 2, the upper lug 95 is on the center projection 93 and the lower lug 96 is on the rear projection 92. Thus, the lower lug 96 produces clockwise (as viewed in FIG. 2) pivoting of the bail 78 about the pin 79 and the upper lug 95 produces counterclockwise (as viewed in FIG. 2) pivoting of the bail 81 about the pin 82.

Therefore, when the interposer 87 of FIG. 2 is activated, the selector cam 50 is positioned for cooperation with the finger 56 on the link 48. This disposes the finger 49 on the link 48 for cooperation with the cam surface 41 so that three units of motion are imparted to the arm 18 when the drive cam 30 rotates through one revolution.

The counterclockwise (as viewed in FIG. 2) pivoting of the bail 81 disposes the cam 51 for cooperation with the finger 64 on the link 38. This positions the finger 39 on the link 38 for cooperation with the cam surface 42 so that the one unit of motion is imparted to the modifying link 21 during the revolution of the cam 30.

Since the bail 84 remains stationary when the interposer 87 of FIG. 2 is activated, the selector cam 52 is not moved. Accordingly, the selector cam 52 remains disposed between the fingers 69 and 70.

Thus, when the interposer 87 of FIG. 2 is activated, the type element 10 is rotated clockwise two units of motion as indicated in the foregoing table. Therefore, the interposer 87 of FIG. 2 is coded to produce two units of clockwise motion of the type element 10.

Each of the other of the interposers 87 has a different arrangement of the upper lug and the lower lug 96 on the three projections 92-94. These produce different amounts of rotation of the type element 10.

For example, when the upper lug is on the rear projection 92 and the lower lug 96 is on the center projection 93, the type element 10 is rotated two units counterclockwise since three units of motion are imparted to the modifying link 21 and one unit of motion to the arm 18.

' Considering the operation of the present invention, one of the keylevers (one shown at 88) is actuated to select the particular type 16 on the type element 10 that is to be printed. This can cause movement of one of the selector cams 50-52 for cooperation with one of the fingers 55, 64, and 69 on the link 38 and one of the other of the selector cams 50-52 for cooperation with one of the fingers 56, 65, and 70 on the link 48. Of course, none of the selector cams 50-52 is moved if the selected type 16 is at the home position of the type element 10.

The selector cams 50-52 are activated during the initial 30 of rotation of the print shaft 31'. During this time, each of the surfaces 40-43 of the drive cam 30 is at a common dwell.

If it is assumed that the keylever 88 of FIG. 2 is depressed, the interposer 87 is advanced to the left in FIG. 2 by one of lobes 97 and 98 on the filter shaft 91 engaging end 99 of the interposer 87 after the interposer 87 has been pivoted clockwise (as viewed in FIG. 2) about a rod 100. This movement of the interposer 87 causes the lower lug 96 on the rear projection 92 to engage the bail 78 to pivot it counterclockwise (as viewed in FIG. 1) to push the rod 77 toward the lever 76.

When the bail 78 is pivoted counterclockwise (as viewed in FIG. 1), the stud 80 on the end of the bail 78 drives the rod 77 toward the lever 76 through being connected thereto. When this occurs, a latch spring 107 moves beneath the stud 80 to retain the selector cam 50 in engagement with the finger 56 on the link 48. A similar arrangement exists for the bail 81 except that its latch spring is disposed above its stud since the bail 81 is pivoted in the opposite direction to the bail 78.

The latch spring 107 holds the bail 78 in the position in which the selector cam 50 engages the finger 56 on the link 48 for approximately of the print cycle. At this time, a latch release lever 108 is activated through a cam (not shown) on the print shaft 31' or another shaft, which is driven during each print cycle, to move the latch spring 107 out of the position in which it holds the bail 78 in its activated position.

When this occurs, a homing spring 109, which is fixed to a portion of the fixed frame of the typewriter, returns the bail 78 to its home position. This also returns the torque bar 60 to the home position whereby the selector cam 50 is returned to its neutral position in which it does not engage either of the fingers 55 and 56.

However, because of the force of the spring 63, the finger 49 is urged against the side of the adjacent surface 40 of the drive cam 30 while riding on the cam surface 41 until the completion of the print cycle. Thus, even though the selector cam 50 is no longer cooperating with the finger 56, the finger 49 remains in engagement with the cam surface 41 of the drive cam 30 until the completion of the print cycle. The finger 39 is similarly retained in engagement with the cam surface 42 of the drive cam 30 because of the force of the spring 61 until the completion of the print cycle.

It should be understood that a similar arrangement is employed with the bail 81 to return it to its home position at the same time. While the bail 84 is not activated during depression of the keylever 88 of FIG. 2, it also has the same arrangement ofa latch spring, a latch release lever, and a homing spring.

When another of the keylevers is selected, a different one of the types 16 on the type element is selected through positioning the bails 78, 81, and 84 in some other arrangement. The selection of a particular one of the types 16 has been previously described through the particular units of motion imparted to the arm 18 and to the modifying link 21 from the drive cam 30 during a print cycle.

Referring to FIG. 3, there is shown a pneumatic mechanism for positioning the type element 10 at the printing position. In this embodiment, the printing element 10 does not return to the home position at the end of each print cycle.

The arm 18 has a rod 110 attached thereto and extending within a cylinder 111. The rod 110 has a piston 1 12 on its end and disposed within a chamber 113 in the cylinder 111. The cylinder 111 has a second chamber 114 formed therein and within which is disposed a piston 115 on the end ofa rod 116, which is pivotally connected to a portion 117 of the carrier.

Pressurized air may be introduced into the chamber 114 through a passage 118 or a passage 119. Whenever the pressurized air is introduced in one of the passages 118 and 119, the chamber 114 is vented through the other of the passages 118 and 119.

Likewise, pressurized air may be introduced into the chamber 113 through a passage 120 or a passage 121. When the air is introduced into the chamber 113 through the passage 120, the chamber 113 is vented through the passage 121 and vice versa.

The modifying link 21 is connected to a rod 122, which has a piston 123 on its opposite end and disposed within a chamber 124 in a cylinder 125. The cylinder 125 has a second chamber 126 formed therein within which is disposed a piston 127. The piston 127 is connected to one end of a rod 128, which is pivotally connected to a portion 129 of the carrier.

Pressurized air may be introduced into one end of the chamber 124 through a passage 130 and into the other end through a passage 131. When the pressurized air is supplied to the chamber 124 through the passage 130, the chamber 124 is vented through the passage 131 and vice versa.

Likewise, pressurized air may be supplied to one end of the chamber 126 through a passage 132 and to the other end of the chamber 126 through a passage 133. When the pressurized air is supplied to the chamber 126 through the passage 132, the chamber 126 is vented through the passage 133 and vice versa.

As shown in FIG. 3, the supply of pressurized air to the chamber 114 is controlled by a rotatable valve 134, which is rotatably supported in a housing 135 on the fixed frame of the typewriter. A spring 136, which is secured to the housing 135, continually urges the rotatable valve 134 to the position shown in FIG. 3 wherein a pulse of pressurized air is supplied through a passage 137 in the valve 134 and a passage 138 in the housing 135 to a hose 139, which connects the passage 138 with the passage 118. This pushes the piston to the right in the chamber 114 of the cylinder 111. At this time, the chamber 114 is vented through the passage 119, a hose 140, a passage 141 in the valve housing 135, and a vent passage 142 in the rotatable valve 134.

When it is desired to supply a pulse of pressurized air to the chamber 114 through the passage 119 and to vent the chamber 1 14 through the passage 1 18, the rotatable valve 134 is rotated clockwise against the force of the spring 136. This positions the supply passage 137 in alignment with the passage 141 in the valve housing 135. It also connects a vent passage 143 in the valve 134 with the passage 138 in the valve housing 135. As a result, the pulse of pressurized air is supplied through the passage 119 to the chamber 114 and the chamber 114 is vented through the passage 118 whereby the piston 115 is moved to the left end of the chamber 114.

The rotatable valve 134 is moved clockwise whenever an interposer 144 is activated by a keylever such as the keylever 88 in the embodiment of FIGS. 1 and 2. When the interposer 144 is moved, a projection 145 on the interposer 144 pulls a bail 146, which is connected to the valve 134 to rotate the valve 134 clockwise. When the interposer 144 is released from holding the bail 146 by the interposer 144 moving to the left, the bail 146 is retained in the position in which it holds the valve 134 so that the passage 137 communicates with the passage 141 until the selected type 16 on the type element 10 is printed.

The bail 146 may be retained in this position by any suitable latching means; thus, a latching arrangement like the latch spring 108 and the latch release lever 109 could be employed, for example. When the lever 109 is released, the spring 136 returns the valve 134 to the position of FIG. 3 but there is no pulse of pressurized air to the passage 137 until the next print cycle. In the next print cycle, the valve 134 could again be rotated clockwise or remain in the position of FIG. 3 depending on the type 16 that is to be selected.

It should be understood that the passages and 121 are connected through another rotatable valve, which is like the rotatable valve 134, to the pressurized air source and the atmosphere. Thus, the piston 112 can be disposed at either end ofthe cylinder 113.

Likewise, the passages and 131 are connected through a rotatable valve, which is like the rotatable valve 134, to the pressurized air source and the atmosphere in the same manner as the passages 118 and 119 are connected to the rotatable valve 134. Thus, the piston 123 can be positioned at either end of the cylinder 124.

The passages 132 and 133 also are connected through a rotatable valve, which is similar to the valve 134, to the pressurized air source and the atmosphere. Thus, the piston 127 can be disposed in either end of the chamber 126 depending upon the position of the rotatable valve, which controls the pulse of pressurized air to the chamber 126.

The lengths of the chambers 113, 114, 124, and 126 are different so that different amounts of movement are imparted to the piston rods having their pistons disposed therein. Thus, with the chamber 114 deemed to have a length for generating one unit of motion, the chamber 126 has a length equal to two units of motion, the chamber 124 has a length equal to three units of motion, and the chamber 113 has a length equal to four units of motion.

Whenever a pulse of pressurized air is introduced into the chamber 114 through the passage 119 with the piston 112 in the position shown in FIG. 3 due to a pulse of air supplied through the passage 120, the cylinder 111 is moved to the right one unit of motion. Since the piston 112 is bearing against a dividing wall 147 of the cylinder 111, one unit of clockwise motion is transmitted to the arm 18 to cause one unit of clockwise rotation of the gear 15. It should be understood that the piston 123 is at the left end of the chamber 124 and the piston 127 is at the right end of the chamber 126 as shown in FIG. 3.

If a pulse of pressurized air also is introduced into the passage 121 at the same time that the pulse of pressurized air is introduced into the passage 118, there would be a total of five units of clockwise motion transmitted to the arm 18. This would position the gear five clockwise units if the pulses of pressurized air are supplied to the chamber 124 through the passage 131 and to the chamber 126 through the passage 133 to retain the pistons 123 and 127 in the position of FIG. 3.

Likewise, the motion to the modifying link 21 from the rod 122 depends upon where the pulses of pressurized air are supplied to each of the chambers 124 and 126. Thus, if a pulse of the pressurized air is supplied to the chamber 126 through the passage 132 while a pulse of the pressurized air is supplied through the passage 131 to the chamber 124, the cylinder 125 is moved to the right so that the modifying link 21 is pivoted two units clockwise with the pistons 112 and 11S disposed as shown in FIG. 3. This causes the gear 15 to rotate two units counterclockwise.

Similarly, if pulses of pressurized air are supplied to the passages 130 and 133, three units of clockwise motion are imparted to the modifying link 21 from the rod 122. This causes the gear 15 to rotate three units of motion counterclockwise if the pistons 1 12 and 115 are in the position of FIG. 3.

The units of rotation of the type element 10 and the direction of rotation are produced by the following relations between the input pulses of pressurized air:

Accordingly, each of the interposers (one shown at 1441) has projections thereon equal to the number of the bails (one shown at 146) to be operated to move the desired number of rotatable valves (one shown at 134) to position the selected type 16 for printing. It should be understood that one of the interposers would not have any of the projections thereon since there would be no movement of any of the rotatable valves when it is desired to rotate the type element 10 five units of motion counterclockwise. Likewise, when it is desired to rotate the type element 10 clockwise five units of motion, the interposer would have four projections thereon to actuate all four of the rotatable valves.

Accordingly, since a pulse of pressurized air is supplied to the passage (one shown at 137) in each of the rotatable valves (one shown at 134) during each print cycle, each of the chambers 113, 114, 124, and 126 receives a pulse of pressurized air during each print cycle. The particular side of the piston to which the pulse of pressurized air is supplied is determined by the position of the rotatable valves (one shown at 134). Thus, each of the types 16 on the type element 10 is digitally selected.

An advantage of this invention is that a compact mechanism is provided for selecting a type on a type element. Another advantage of this invention is that the conversion from digital to analog occurs at the carrier.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A printer having a type element carrying a plurality of types at regular intervals spaced along a path, means cooperating with said type element for defining a printing position in cooperation therewith, means mounting said type element for movement along said path to position a selected one of said types at the printing position wherein the improvement comprises:

a positioning member connected to said type element for movement therewith relative to the mounting means;

a first gear connected to said positioning member for motion therewith relative to the mounting means;

a second gear positioned in operative mesh with said first gear;

a modifying link mounted for pivotal motion about an axis that is fixed with respect to said positioning member;

axle means mounting said second gear for pivotal motion about an axis that is displaced from said positioning member, said axle means being mounted on said modifying link;

first input means for positioning said modifying link to any of a predetermined plurality of pivotal positions about said positioning member;

and second input means for positioning said second gear to any of a predetermined plurality of pivotal positions relative to said axle means.

2. A printer as defined in claim 1 including single drive means to synchronously move both of said first and second input means.

3. A printer as defined in claim 2 wherein:

said single drive means comprises a rotatable cam having a plurality of different cam surfaces;

said first input means has means cooperating with said cam;

said second input means has means cooperating with said cam;

selector means to position said cooperating means of said first input means on one of the cam surfaces of said cam and said cooperating means of said second input means on one of the cam surfaces of said cam;

and means to control said positioning means.

4. A printer as defined in claim 3 in which:

each of said first input means and second input means comprises lever means;

said lever means of said first input means being connected to said modifying link;

said lever means of said second input means being connected to said second gear;

said lever means of said first input means has said cam cooperating means of said first input means connected thereto;

and said lever means of said second input means has said cam cooperating means of said second input means connected thereto.

5. A printer as defined in claim 4 in which said selector means includes:

a plurality of selector cams;

a pair of elements for cooperation with each of said selector cams, one of said elements of each pair being mounted on said first input means and the other of said elements of each pair being mounted on said second input means;

and means for selectively positioning each of said selector cams relative to said pair of elements cooperating therewith to dispose said selector cam in a first position in which said selector cam engages neither of said elements, a second position in which said selector cam engages said element on said first input means, and a third position in which said selector cam engages said element on said second input means.

6. A printer as defined in claim 3 in which said selector means includes;

yieldably exerting an opposing force against each of said first input means and said second input means.

and means for selectively positioning each of said selector cams relative to said pair of elements cooperating therewith to dispose said selector cams in a first position in which said selector cam engages neither of said elements, a second position in which said selector cam engages said element on said first input means, and a third position in which said selector cam engages said element on said second input means.

7. A printer as defined in claim 3 in which:

said mounting means for said type element is a movable carrier;

and stationary means supports said control means.

8. A printer as defined in claim 2 in which:

said first gear has teeth around its entire periphery;

and said second gear has teeth along only a sector thereof 15 and meshing with said teeth on said first gear.

9. A printer as defined in claim 2 in which:

each of said first input means and said second input means comprises lever means;

said lever means of said first input means being connected to said modifying link;

and said lever means of said second input means being connected to said second gear.

10. A printer as defined in claim 2 including resilient means 11. A printer as defined in claim 2 in which said first input means and said second input means produce rotation of said first gear in opposite directions to rotate said first gear in a direction depending on which of said first input means and said second input means produces the input of largest magnitude and the difference therebetween.

12. A printer as defined in claim 1 including: first driving means cooperating with said first input means to move said first input means to position said modifying link at any of its plurality of predetermined positions;

and second driving means cooperating with said second input means to move said second input means to position said second gear at any of its plurality of predetermined positions.

13. A printer as defined in claim 12 including:

first pneumatic means to control said first driving means;

and second pneumatic means to control said second driving means.

14. A printer as defined in claim 12 in which said first input means and said second input means produce rotation of said first gear in opposite directions to rotate said first gear in a direction depending on which of said first input means and said second input means produces the input of largest magnitude and the difference therebetween.

15. A printer as defined in claim 1 in which:

said first gear has teeth around its entire periphery;

and said second gear has teeth along only a sector thereof and meshing with said teeth on said first gear.

16. A printer as defined in claim 1 in which said first input means and said second input means produce rotation of said first gear in opposite directions to rotate said first gear in a direction depending on which of said first input means and said second input means produces the input of largest magnitude and the difference therebetween.

17. A printer as defined in claim 1 including resilient means yieldably exerting an opposing force against each of said first input means and said second input means.

18. A printer as defined in claim 1 in which:

each of said first input means and said second input means comprises lever means;

said lever means of said first input means being connected to said modifying link;

and said lever means of said second input means being con nected to said second gear. 

1. A printer having a type element carrying a plurality of types at regular intervals spaced along a path, means cooperating with said type element for defining a printing position in cooperation therewith, means mounting said type element for movement along said path to position a selected one of said types at the printing position wherein the improvement comprises: a positioning member connected to said type element for movement therewith relative to the mounting means; a first gear connected to said positioning member for motion therewith relative to the mounting means; a second gear positioned in operative mesh with said first gear; a modifying link mounted for pivotal motion about an axis that is fixed with respect to said positioning member; axle means mounting said second gear for pivotal motion about an axis that is displaced from said positioning member, said axle means being mounted on said modifying link; first input means for positioning said modifying link to any of a predetermined plurality of pivotal positions about said positioning member; and second input means for positioning said second gear to any of a predetermined plurality of pivotal positions relative to said axle means.
 2. A printer as defined in claim 1 including single drive means to synchronously move both of said first and second input means.
 3. A printer as defined in claim 2 wherein: said single drive means comprises a rotatable cam having a plurality of different cam surfaces; said first input means has means cooperating with said cam; said second input means has means cooperating with said cam; selector means to position said cooperating means of said first input means on one of the cam surfaces of said cam and said cooperating means of said second input means on one of the cam surfaces of said cam; and means to control said positioning means.
 4. A printer as defined in claim 3 in which: each of said first input means and second input means comprises lever means; said lever means of said first input means being connected to said modifying link; said lever means of said second input means being connected to said second gear; said lever means of said first input means has said cam cooperating means of said first input means connected thereto; and said lever means of said second input means has said cam cooperating means of said second input means connected thereto.
 5. A printer as defined in claim 4 in which said selector means includes: a plurality of selector cams; a pair of elements for cooperation with each of said selector cams, one of said elements of each pair being mounted on said first input means and the other of said elements of each pair being mounted on said second input means; and means for selectively positioning each of said selector cams relative to said pair of elements cooperating therewith to dispose said selector cam in a first position in which said selector cam engages neither of said elements, a second position in which said selector cam engages said element on said first input means, and a third position in which said selector cam engages said element on said second input means.
 6. A printer as defined in claim 3 in which said selector means includes; a plurality of selector cams; a pair of elements for cooperation with each of said selector cams, one of said elements of each pair being mounted on said first input means and the other of said elements of each pair being mounted on said second input means; and means for selectively positioning each of said selector cams relative to said pair of elements cooperating therewith to dispose said selector cams in a first position in which said selector cam engages neither of said elements, a second position in which said selector cam engages said element on said first input means, and a third position in which said selector cam engages said element on said second input means.
 7. A printer as defined in claim 3 in which: said mounting means for said type element is a movable carrier; and stationary means supports said control means.
 8. A printer as defined in claim 2 in which: said first gear has teeth around its entire periphery; And said second gear has teeth along only a sector thereof and meshing with said teeth on said first gear.
 9. A printer as defined in claim 2 in which: each of said first input means and said second input means comprises lever means; said lever means of said first input means being connected to said modifying link; and said lever means of said second input means being connected to said second gear.
 10. A printer as defined in claim 2 including resilient means yieldably exerting an opposing force against each of said first input means and said second input means.
 11. A printer as defined in claim 2 in which said first input means and said second input means produce rotation of said first gear in opposite directions to rotate said first gear in a direction depending on which of said first input means and said second input means produces the input of largest magnitude and the difference therebetween.
 12. A printer as defined in claim 1 including: first driving means cooperating with said first input means to move said first input means to position said modifying link at any of its plurality of predetermined positions; and second driving means cooperating with said second input means to move said second input means to position said second gear at any of its plurality of predetermined positions.
 13. A printer as defined in claim 12 including: first pneumatic means to control said first driving means; and second pneumatic means to control said second driving means.
 14. A printer as defined in claim 12 in which said first input means and said second input means produce rotation of said first gear in opposite directions to rotate said first gear in a direction depending on which of said first input means and said second input means produces the input of largest magnitude and the difference therebetween.
 15. A printer as defined in claim 1 in which: said first gear has teeth around its entire periphery; and said second gear has teeth along only a sector thereof and meshing with said teeth on said first gear.
 16. A printer as defined in claim 1 in which said first input means and said second input means produce rotation of said first gear in opposite directions to rotate said first gear in a direction depending on which of said first input means and said second input means produces the input of largest magnitude and the difference therebetween.
 17. A printer as defined in claim 1 including resilient means yieldably exerting an opposing force against each of said first input means and said second input means.
 18. A printer as defined in claim 1 in which: each of said first input means and said second input means comprises lever means; said lever means of said first input means being connected to said modifying link; and said lever means of said second input means being connected to said second gear. 